Oxidation Resistance at 1 000℃ of Ni-15Cr-5Al-xSi Alloys

Ni-15Cr-5Al-xSi (x=0, 1, 3, 5, mass fraction/%) alloys were prepared by powder metallurgy and then oxidized at 1 000℃ for 100 h. Effects of silicon content on surface phase composition and high temperature oxidation resistance of the alloys were studied. The results show that the alloys with 0 and 1wt% silicon were both anti-oxidant grade, and the alloys with 3wt% and 5wt% silicon were both complete anti-oxidant grade. After oxidation, NiO and Al₂O₃ oxides were formed on surface of all the four alloys; also, NiAl₂O₄ and Cr₂O₃ existed on surface of the alloys with silicon content of 0 and 1wt%, and a small amount of Cr₂O₃ and NiCr₂O₄ were found with silicon content of 3wt% and 5wt%. The oxide scale on surface of the alloy with 5wt% silicon was flat and had a dense structure, and the oxide particles were fine and homogeneous. The alloy with 5wt% silicon had the best oxidation resistance at high temperature.